The City of London has been rocked by scandal as a number of prominent lawyers, including Christopher Grierson, are to face investigations into alleged financial irregularities. Photograph: Photolibrary/Corbis

Until last month, Christopher Grierson was one of the most respected lawyers in the country. "A likeable, restrained and quietly spoken man," the former Hogan Lovells partner was runner-up (pdf) in the 2010 lawyer of the year awards after starring roles advising on the Bernard Madoff fraud case and the aftermath of the Lehman Brothers collapse.

No one knew Grierson, 59, was also busy amassing a total of £1m in false expenses, pocketing an annual £250,000 over a four year period.

He did so mainly by booking flights on his credit card and claiming the value back from the firm – although they were subsequently cancelled.

Grierson's luck ran out earlier this year when an internal investigation – initiated for reasons that remain a mystery – revealed what was happening. He was sacked a few weeks ago and later reported to the police.

Since news of the scandal broke it has emerged that two further City lawyers are also under investigation for financial irregularities.

Former Ince & Co partner Andrew Iyer is at the centre of allegations of a £3m fraud involving clients' money, and ex-Addleshaw Goddard partner Mark Gilbert is alleged to have made false expenses claims.

It does not stop there. According to Frank Maher, a partner at Legal Risk, a leading law firm in the specialist field of professional regulation, another three City lawyers are being investigated by the Solicitors Regulation Authority (SRA) – with one of the cases involving "one of the biggest law firms in the country, millions of pounds and a truly unbelievable set of facts".

Maher adds that this is the busiest period he has ever known for breaches of conduct by large law firms.

The obvious explanation for this apparent hike in crookedness is that City lawyers are short of cash. But while most have been hit by recession-driven falls in profits and the rise in top rate income tax to 50%, they still tend to be pretty comfortably off.

Grierson, for example, was on £830,000 a year and seemingly in such good financial shape that he was able to repay the £1m he wrongly claimed almost immediately.

In such circumstances, risking everything for some extra cash seems like insanity – or at least insane greed.

Perhaps, though, insane greed is not so mad in the context of money-obsessed modern corporate law, where success is now measured in terms of how much dosh the highly competitive individuals drawn to this branch of the profession make, rather than how well they balance the commercial considerations of their clients with serving justice – as used to be the case to a far greater extent before the boom of the late 1990s and early 2000s.

Grierson's salary was huge, but there are partners in the City on £2m plus, not to mention senior bankers whose earnings often dwarf even that sort of sum.

Innocent until proven guilty, Grierson's intentions may not have been dishonest, but as one of the UK's star lawyers who had brought in a string of big name clients to his firm, it's possible he felt his efforts were not sufficiently valued.

If this was the case, it must have been quite a source of frustration for someone whose 24/7 career would have bound his self esteem especially closely to the office.

Is it really such a stretch to imagine a seriously disgruntled person, who works in an environment where money is the only benchmark of performance, putting their hand in a cookie jar to which they have free access?

It might not even have been such a big leap for a classic alpha City type like Grierson, who in 2001 prophetically told the Lawyer magazine, in response to a win in a big case, that "it's quite a challenge when you take on the establishment, and quite a challenge taking on big organisations that think they can protect themselves fairly well – sometimes they can and sometimes they can't".

As gossip rages around the City about where the next scandal will appear, the focus is moving to what firms can do to protect themselves.

With accounts rules breaches and dishonesty-related offences now making up over half (pdf) of all substantiated allegations against solicitors, an obvious starting point would be for them to tighten up their internal money-handling controls. A simple rule against self-certification of expenses would have been enough to stop Grierson.

Surprisingly, though, there remains a reluctance to act, with a quaint consensus among City law firm partners that moral fibre remains as high as ever.

Only 18% of respondents to a recent survey by Legal Week magazine conducted in response to the news about Grierson suggested the quality of financial monitoring and governance frameworks at major law firms "could be better".

Meanwhile, 72% said they believed law firm partners have better ethical standards than their counterparts in banking and accountancy.

A comparison with the banking sector may not be the best guide to standards, but the message behind the statistics is clear: lawyers have somehow managed to convince themselves that there is no ethical downside to greater alignment with the values of their corporate clients – an approach that has seen their salaries spiral over the last 15 years as they redefined themselves as big picture dealmakers rather than annoying sticklers for inconvenient detail.

At best, refusing to admit that this new style of working exposes them to more risk is misplaced loyalty to an outdated professional idyll. At worst, it's intellectual dishonesty.

Either way, this have-your-cake-and-eat-it mentality was more than evident in the reader comments to the original story about Grierson on thelawyer.com, with many of the lawyers who posted expressing support for the disgraced "gentleman".

As one put it: "Chris was always the consummate professional, hard-working, a fantastic leader and a gentleman. I cannot imagine what prompted this behaviour and am sorry that he is having to endure this."

Time for City lawyers to follow MPs in coming to terms with the fact that they are as susceptible to temptation as anyone else – if not more so.

Alex Aldridge is a freelance journalist who writes about law and education